This invention relates to a method for operating an electrostatic precipitator with a DC voltage, the level of which can be changed, and superimposed DC voltage pulses, in which at least one of the parameters, pulse amplitude, pulse width, pulse repetition frequency and rate of rise of the pulses can be varied.
As a rule, electrostatic precipitators are nowadays operated with a high DC voltage which is generated by rectification from an AC power network.
It is furthermore known in the art to operate electrostatic precipitators with high frequency AC current or with low frequency AC current below 50 Hz (See column 1 of German Pat. No. 14 57 140.)
The use of pulsating DC voltage as the supply voltage is also known in the art; the pulsating DC voltage can be obtained by superposition of a DC voltage and a sinusoidal AC current, or by means of bridge rectification. (See column 1 of German Pat. No. 14 57 140.)
Another method known in the art is to vary the frequency of the pulsating DC voltage half waves at the electrostatic precipitator in such a manner that a predetermined breakdown frequency per unit time remains constant. (See, for instance, German Pat. No. 14 57 140.)
A DC voltage with superimposed voltage pulses has also been used. (See U.S. Pat. No. 4,133,649.)
Theoretical considerations and tests regarding this subject can also be found, for instance, in the journal: "Staub-Reinhaltung der Luft", no. 36, 1976, no. 1, pp. 19-26.
It is evident from the above-mentioned literature references that those skilled in the art have recognized that the amplitude of the DC voltage and pulses, the pulse frequency and the flank slope of the pulses play a part.
Since, in addition to these factors, the nature of the dust to be precipitated in such a case also plays an important part, it is understandable that it has not yet been possible, to date, to specify an optimum of the operating parameters which would fit each respective operating condition.
It is an object of the present invention to describe a relatively simple optimizing method, including a permissible dust load in the purified gas.